Indicating device



.A. BLOCK INDI CATING DEVICE Jan. 12,1926. 1,569,255

Filed June 12. 1922 2 Sheets-Sheet 1 L: N a;

/N l/E/V TOR? ABRAHAM BLOCK A TTO/PNEYS.

Jan) 12 1926.

A. BLOCK INDICATING DEVICE Filed June 12. 1922 Patented Jan. 12, 1926.

UNITED STATES PATENT OFFICE.

ABRAHAMELOCK, OF SAN FRANCISCO, CALIFORNIA, ASSIGNOR TO THE NATIONAL CASH REGISTER COMPANY, OF DAYTON, OHIO, A CORPORATION OF OHIO INDICATING DEVICE.

To a?! 40710712,. it may concern Be it known that I, ABRAHAM BLOCK, a citizen of the United States, residing at the city and county of San Francisco and State of California, have invented new and useful Improvements in Indicating Devices, of which the following is a specification.

This invention relates to an indicator for telephone switch boards, annunciators, etc., such as employed in hotels, department stores and the like, and especially to an indicator whereby the calls or circuits established will be consecutively indicated in the order received.

Practically all hotels, stores and large concerns, employ a main telephone switch board or exchange and one or moreoperators who receive and plug in all calls whether incoming, outgoing or intercommunicating. The calls entered are in practically every instance visibly indicated by lights on the switch board and it often happens during busy hours that many lights will accumulate before the operator or operators have an opportunity to plug in or in other words connect the proper lights. No means are employed at the present time for indicating or recording the calls in the order received. It therefore often happens that the last calls are first attended to, while others are unintentionally delayed. Such delays are not on y annoying and undesirable, but are also the cause of innumerable complaints and dissatisfaction. This is obviously objectionable.

The object of tne present invention is to generally improve switch boards of this character and especially to provide an indicator which will not only visibly indicate the number of calls entered but also visibly indicate the order in which they are re ceived, thus generally remedying the situa tion above referred to and at least reducing the delays encountered to a minimum. Further objects will hereinafter appear.

One form which my invention may assume is exemplified in the following description and illustrated in the accompanying drawings, in which- I Fig. 1 is a diagrammatic view of a switch board and a series of teleihoncsconnected therewith.

phones, as indicated at 1.2, 13 and Fig. 2 is a side elevation partially in section of the indicator actuating mechanism.

Fig. 3 is a cross section of Fig. 2 taken on line Referring to the drawings in detail, and

particularly to Fig. 1, A indicates a main telephone switch board such as employed in the telephone exchange of hotels, department stores and other commercial concerns. The switch board is provided with a series of acks generally indicated at 2, 3, and 4, and one or more plugs as indicated at 5 whereby certain circuits may be established and others broken. Cooperating with each jack is a pair of indicating lights generally indicated at 6, 7, 8, 9, 1O andll. A circuit through the lights 6, 8 and 10 is established through outside telephones as indicated at .12, 13 and 14, and a circuit is simultaneously established through cooperating relays indicated. at 15, 16 and 17 the relay 15 cooperating with the light ,6, the relay 16 with the light 8, and the relay 17 with the light 10. The lights 6, 8 and 10 are provided for the purpose of indicating the number of calls entered, while the lights 7, 9 and 11 are employed for the purpose of indicating the order in which the calls were entered as will hereinafter be described. The lights 7, 9 and 11 are actuated by the mechanism generally shown in Figs. 2 and 8, which will hereinafter be referred to.

The switch board A, as previously stated, is provided with one or more plugs 5 and connected therewith is a receiver 18 and a transmitter 19 which are actuated by a battery 20. In this instance only one plug, with connected receiver and transmitter, is shown, but it should be understood that one or more may be provided if desired. I have similarly only illustrated three jacks, as indicated at 2, 3 and 4, and three outside telephones, as indicated at 12, 13 and 14, but any additional number of outside telephones and jacks may be provided, the number employed depending entirely upon the size. of the system, etc.

For the purpose of clearly describing the invention we will suppose that the present system connects a series of sub-station tele- 14, with a central station telephone as indicated at 18 and 19, and that one or more of the substation telephones may desire to communicate with the central station at approximately the same time. If this is the case it should. be obvious that each sub-station telephone should be answered as quickly as possible and that each call should be taken up in its order. F or instance the telephone system shown might be connected with an authorizing otlice and one sub-station may require certain information, while other sub stations require different information. Hence each call should be given its turn to avoid unnecessary delay, etc. In the present instance we will suppose that the substation indicated at 12 desires to communicate with the central station. if this is the case the person stationed at the station indicated at 12 will only remove the receiver and place it to her or his ear and then wait until the central station answers. The moment the receiver is removed a circuit is established through the hook switch indicated at- 31, which can be traced as follows: Commencing with the hook the current passes through wire 22, contact 23 of the jack 2, contact 24 cooperating therewith, light 6, wire 25, relay 15, battery 26, wire 27, contact 28 of the jack 2 and the cooperating contact 29, wire 30, transmitter of substation 12, the receiver connected therewith, and the hook switch 31, thus completing the circuit, which results in two functions: first that of lighting the light 6, and secondly that of energizing the relay 15. The moment the light is indicated on the board, the operator inserts the plug .5 in the jack 2 and thereby breaks the circuit through the contacts 23, 24, 28 and 29. This causes the light 6 to go out and the relay to he de-energized, and it simulta neously establishes a circuit through the battery and the transmitter 19 and the receiver 18, in this manner placing the operator at the central station in talking comniuia .rion ith the person desiring information from sub-station 12. This circuit is called the talking circuit and can be traced as iollows:

turrent from the battery passes through wire 37, plug contact 38, contact 29, wire 50, the receiver of station 12 and the transmitter indicated. Current then passes through the hook switch 31, wire 22, contact 2?), the plug contact ill) and wire 40, which completes the circuit through the transmitter 19, the receiver 18 and the battery 2 ll'hcn the talking circuit has been established, the operator at the central. station will immediately notify the person desiring inforn'iation from suh-sttion 12 and conversation regarding the information desired may proceed. While this conversation is taking place, or while the operator at the central station is looking up the information, other calls may enter, for instance calls may be entered from sub-stations 13 and 14, and these calls will be indicated on the switch board A loy the lights 8 and 10. The operator at the central station may not have noticed the order in which the lights appeared and will for this reason not know which station should be answered first or last. The operator will therefore merely convey the information desired by sub-station 12 and will immediately remove the plug 5 when such information has been transmitted, thus disconnecting the substation 12. The next sub-station desiring information will then be plugged in and, in order to determine which sub-station should be answered first, an indicating mechanism conveying such information is employed.

The indicating mechanism is actuated by the relays 15, 16 and 17, and these in turn energize magnets such as shown at 41, and 43; the magnet 41 cooperating with relay 15 and light 7, magnet 42 with relay 16 and light 9, and magnet with relay 17 and the light 11. The magnets 41, 42 and 43 in turn actuate individual switch levers generally indicated at 44, 45 and 46, and these in turn actuate a master lever gener ally indicated at 47, the master lever serving the function of intermittently closing circuit-s through the lights 7, 9 and 11, and in such a manner that the lights 7, 9 and 11 will appear in the same order as the calls are entered from the sub-stations 12, 13 and 14. For instance if sub-station 13 entered its call before the sub-station 14, then light 9 will appear first, and secondly the light 11, in this manner showing the operator of the central station the order in which the calls are entered and the order in which they should be answered. The indicator actuating mechanism, as previously stated, is shown in detail in Figs. 2 and 8. The mechanism cons a; of an elongated housing B, in wl'iich, rurnalled a shaft C. This shaft extends longituiilinally through the casing and is preferably constructed of an insulating material, such as fiber, vulcanized rubber and the like. The shaft supports a series of ratchet gears, indicated at 50,, 51 and These gears are spaced from each other, as shown, and each gear is keyed or otherwise secured to the shaft. The shaft also supports a series of pinions indicated at (30, 61 and and each pinion in turn inter meshes with gear segments 70, T1 and 72. These gear segments are freely turnable on a supporting shaft 78 extending longitudinally through the casing, and each segment is connected with a tension spring 74 as shown in Fig. 3. The segments are suitably secured again. .t endwire movement on the shaft 73. while the pinions 60, 61 and lit are slidahly mounted on the shaft C and are freely turnable thereon. Each pinion'60,

v at 77.

61 and 62 is provided with a grooved shitting collar 75, and each collar is straddled or engaged by a rocker arm 76 pivotally supported in the lower portion of the casing as Each rocker arm is in turn provided with a horizontally extending arm 78, and these arms are connected with helical tension springs 79, the function of which will hereinafter be described.

Formed as an integral part of each gear 60, 61 and 62, or otherwise secured thereto, are switch arms 44, 45 and 46. These arms terminate in pawls 66 at their upper ends, which are adapted to be moved into or out of engagement-with the respecive ratchet T621115 50, 51 and that is the pawls 6 3 are Iormed on the sides of the arms 44, 45 and 46, and they are moved into and out of engagement with the respective ratchet 50, 51 and 52 when endwise movement is imparted to the pinions 60, 61 and 62. The upper ends of the pawls are extended as shown in Figs. 2 and 3, and they are adapted to consecutively engage the master switch arm indicated at 47. This switch arm consists of a horizontally disposed bar, perhaps best illustrated in Fig. 2, which is supported by a pair of arms 67. These arms are turnably mounted on the shaft C and are insulated from the housing B and a retaining ratchet wheel 53 suitably pinned to the shaft C. A circuit may however he established through the master switch arm and the switch arms 44, 45 and 46 in consecutive order and a wire 80 is therefore connected to the master switch arm, while the respective wires 81, S2 and 83 are con nected to the segments 70, 71 and 72. These segments are in circuit with the arms 44., 45 and 46, as the segments proper are constructed of metal, as are also the pinions 60, 61 and 62 and the switch arms 44,45 and 46.

The operation of the indicator actuating mechanism will be as follows: We will again suppose that a call was made through sub-station 12 and that the light 6 and the relay 15 were energized by the circuit established therethrough. In that instance armature 15 of relay 15 will be attracted and a circuit will be closed through a switch 90, a battery 91 and magnet 41, which can be traced as follows:

Current from the battery 91 passes through switch 90, armature 15*, wire 92, magnet 41 and then returns to the battery, completing the circuit. When this magnet is energized, an armature cooperating therewith and indicated in Figs. 2 and 3 by the numeral 93 will be attracted. This armature is carried by a lever 94 pivotally supported in the casing, as at 95. The outer end of this lever normally engages the upper end of the shifting lever 76 and holds it in a vertical position, but when lever 94 is raised or attracted by magnet 41, shifting lever 76 swings over to the position shown in Fig. 2 and thereby moves the collar 7 5, pinion 60 and switch arm 44 into the position shown in Fig. 2. This position causes the pawl 66 to engage the ratchet gear 50, and it also causes a pawl 96, carried by the lever 94,to engage the ratchet gear 50 and impart a partial turning movement thereto, which we will term a one-step movement. This one-step movement of the ratchet gear and the pawl 66 about shaft C will cause the upper end of the switch arm 44 to engage the master switch arm 47 and thus close a circuit through the light 7 which can be traced as follows:

Commencing with battery 26 the current passes through wire 27, a wire 98, wire 99, light 7, wire 81, segment 70, pinion 60, switch arm 44, switch arm 47 and wire 80 which completes the circuit through the battery 26, thus when only one sub-station calls, two lights will appear, first that indicated at 6 and then that indicated at 7, that is these two lights will appear if sub-station 12 alone calls, while lights 8 and 9 will appear if substation 13 happens'to be the only station that calls, and similarly lights 10 and 11 will appear if sub-station 14 happens to be'the only one that calls. Again if the operator at the central station is talking with one substation and one or more calls enter, two lights will appear for the first station calling and only one light for the next or succeeding stations calling. Further it may here be stated that only one of the lights 7 9 and 11 will appear at any one time and that these lights will appear in the order in which the calls are received. This will be readily understood when the followingdescription is considered:

Heretofore it was stated that a circuit through battery 91 and magnet 41 was established simultaneously with the closing of the circuit through the relay 15 and the light (3, and that the circuit through the relay 15 and the light 6 was broken the. moment plug 5 is inserted in the jack 2. If this is the case it is obvious that a circuit through the magnet 41 and the battery 91 will also be broken as de-energization of relay 15 will cause the switch to open. This is important as lights 6 and 7 will accordingly go out in unison when a plug is inserted, and it will permit the actuating mechanism to return to normal position. The normal position of this mechanism is assumed when the master switch arm 47 engages a stopmember 1.00 and when the switch arms 44, 45 and 46 engage a stop rod 101, which eX- tends longitudinally through the casing and is suitably supported therein. The return of the mechanism to normal position is caused themoment magnet 41 is de-energized as lever 94 will be depressed or lowered by means of a spring 102, see Fig. 3, This depressing movement of lever 94 causes the outer end thereof to engage the upper end of the shifting lever 76. The upper end thereof is cam shaped, as shown in Fig. 2, and it is therefore rocked to a vertical position when engaged by the outer end of lever 94. This movement of the shifting lever 76 is transmitted through the shifting collar to the gear 60 and the switch arm 44, and the pawl 66 carried thereby is therefore released with relation to the ratchet gear 50 and the switch is returned to engagement with the stop rod 101 as the pull exerted by spring 7 4 and the segn'ient 70 will cause rotation of gear 60 and switch arm 44, causing this to swing back into engagement with the stop rod 101. The master switch 47 will also move back into engagement with the stop 100, such ret rograde or reverse movement of the master switch arm 47 being caused by a coil spring 103, which engages one of the arms 67. At this point of the description it should be stated that the master switch arm 4'? may be advanced by any one of the switch arms 44, 45 or 46, and in fact must be advanced by one or the other of these arms; further, that the master switch arm is returned to normal position, or in other words to engagement with the stop 100 when the switch arm which engages the same is released and returned to normal position.

Vi e will now suppose that while the operator at the central station is communicating with sub-station 12, that two calls are entered, one from substation 13 and one from sub-station 14. If this is the case lights 8 and 10 will appear on the switch board and the operator will therefore know that two calls are waiting his or her attention. The operator will also know which station called first as .two lights will appear for the first sub stationcalled. lVe will now suppose that sub-station 13 entered the first call while the operator was busy with substation 12. and it therefore obvious that light 8) will. next aiipear and then light 11, thus showing the operator the order in which the calls were received. This consecutive lighting of the lights 7, 9 and 11 in the order received is controlled entirely by the mechanism shown in Figs. 2 and 3, and it is particularly controlled by the switch arms 44, and 46 and the master switch arm 47. For the purpose of illustration we stated that substation 13 entered its call prior to sub-station 14 and as such is the case light 8, relay 16 and magnet 42 would atunlly be energized before the light 10, relay 1? and magnet As magnet 42 is energized prior to magnet 43, it can be seen that the armature of magnet 42 will be attracted and that the lever carrying the armature will be raised, thereby shifting the pinion 61 towards the ratchet gear 51, and simultaneously bringing the pawl (36 into engagement with the ratchet gear 51. The pawl 96 of the lever 94 cooperating with the ma net 42 will at the same time impart a one-step turning movement to the ratchet gear 51. No movement will, however, be imparted to the switch arms 44 and 46 at this time as the switch arm has already been released when plug 5 was inserted in jack 2, and switch arm 46 assumes released position and will not be thrown into engagement before the magnet 43 is energized. o will now assume: that sub-station 14 calls and that light 10, relay 1'? and magnet 43 are energized. Pinion 2 will then be shifted towards the ratchet gear and the pawl on the switch arm 46 will thus engage the ratchet gear 52, and pawl 96 will also engage and impart a second step of movement to the ratchet gear 52, that is all of the ratchet gears shown will turn in unison whenever one of the magnets 41, 42 or 43 is ener ized as the ratchet gears are all secured to the shaft C and must therefore turn in unison. Therefore if switch arm 45 is in engagement with the ratchet gear 51 when switch arm 46 is thrown into engagement, it is obvious that switch arm 45 will advance a second step when switch arm 46 advances its first step. In Fig. 3, the switch arms 44, 45 and 46, are shown in step formation, switch arm being in engagement with the stop rod 101, switch arm 44 having been advanced one step, and switch arm 46 having been advanced two steps.

l vhen switch arm 46 is released it re turns to normal position, or into engagement with the stop rod 101. The master switch arm 47 will also tend to return, but it will only return to a point where it engages the switch arm 44, where it will be stopped. \Vhen it engages this arm, is closes a circuit therethrough and light T will appear, showing the operator that substation 12 is the next station to be answered. it is due to the fact that the switch arnn l. 45 and 40 assume advanced positions with relation to each other that it is possible to establish the circuits in consecutive order through the lights 7, 9 and 11, and in the order received. To further explain this operation we will suppose that there are six sub-stations, six jacks, six rel, and six magnets, and that all sub-stations enter calls at substantially the same time. The first substation which calls will advance the ratchet gears one step. The second sub-station that calls will advance the ratchet gears another step, and so on. In other words by the time the sixth call has been entered, the switch arm which cooperates with the first substation will have advanced six steps, and similarly the master switch arm. Therefore when the operator at the central station plugs in and answers the first station, the

switch arm cooperating therewith will be released and-will return to normal position. The master switch will also return in unison therewith, but only one step, or in other words until it engages the switch arm which has been advanced five steps. It here establishes a circuit through the light in the station which made thesecond call and therefore indicates to the operator that this station. made the second call and should be the second one answered. In this connection it may again be stated that the switch board will show six lights if six calls are simultaneously awaiting an answer, and will only indicate one additional light to show which station should be next answered. 1 r

The system here shown is particularly adapted where a series of sub-station telephones are connected with a central station telephone, and the wiring connections illustrated in Fig. 1 have therefore been shown in connection with this type of system. It is however obvious that this system may be employed in anyother standard telephone system where incoming, outgoing or intercommunicating calls are made, and also that it maybe employed in conjunction with electrically actuated annunciators and similar devices. Further, While the mechanism whereby the indicating lights are actuated is more or less specifically illustrated, I

wish it understood that various changes in form and proportion may be resorted to within the scope of the appended claims, similarly that the materials and finish of the several parts employed may besuch as the experience and judgment of the manufacturer may dictate or various uses may demand. I

Having thus described my invention, what I claim and desire to secure by Letters Patent is 1. An electric circuit controlling system embodyinga central station and a plural ity of sub-stations, a circuit in the central station for each substation, means in each sub-station for establishing or preparing its appropriate circuit in the central station, .said means being so arranged that the first sub-station operated will close its circuit in the central station and succeeding substations operated will only prepare their circuits in the central station and means in the central station for breaking the first circuit established by a sub-station and for automatically closing the prepared circuit of the next sub-station operated.

2. Ina device 'ot the'characterdescribed a central station" andfa plurality of substations, a plurality of electric lights in the central station one cooperating with each sub-station, a second series of lights one for each sub-station, means in each substation for establishing a circuit through the first named light connected therewith, and means in the central station for establishing circuits through the second series of lights in the order in which the first named light ing circuits were established when two or more of said circuits are established.

' 3. In a device of the character described, a central station and a plurality of substations, a plurality of indicators in the central station, one cooperating with each sub-station, a second series of indicators in the central station, one for each sub-station, means in each substation for establishing a circuit through the first named indicator connected therewith, and means in the central station cooperating with the second named indicating means for indicating the order in which the first named indicating circuits were established when two or more circuits are established. 7

-l. In an intercommunicating telephone system of the character described, a central station and a. series of sub-stations, a signal circuit between each sub-station and the central station, means in each sub-station for closing its individual signal circuit, a series of signal circuits in the central station, one for each sub-station, means in the central station for establishing a communicating circuit with the first sub-station establishing a signal circuit, and means cooperating with said means for breaking thecircuit established by said first substation and for automatically closing a circuitv in the central station cooperating with a signal circuit established by another sub-station when two or more substations have established signal circuits. 7 M

5. In an intercommunicat-ing telephone system of the character described, a central station and a series of sub-stations, a signal circuit between each sub-station and the central station, a second series of signal circuits in the central station, one for each substation, means in each sub-station for 010s ing its first named signal circuit, means in the central station for disconnecting each first named signal circuit and for simultaneously establishing a talking circuit,and means actuated by the breaking of a signal circuit for closing one of the second named signal-circuits, said second named signal circuit indicating that other sub-stations have entered calls and said second named signal circuit also indicating the order in which the calls have been entered.

6. In an intercommunicatingelectric system of the character described, a central station and a series of sub-stations,sig11al circuits connecting the sub-stations with the central station indicating the sub-station calling" and also indicating whether one or more sub-stations are calling, and also permitting one or more sub-stations to call substantially at the same time, and a second series of signal circuits, one for each substation adapted to indicate the order in which the sub-stations have entered their calls.

7. In an intercommunicating telephone system of the character described, a central station and a series of sub-stations, a signal circuit between each sub-station and the central station, means in each sub-station for establishing or preparing a circuit through its signal in the central station, said means being so arranged that the first sub-station to call will establish a circuit through its indicating signal in the central station, and succeeding sub-stations calling will only prepare circuits through their indicating signals, and means in the central station for breaking the first indicating signal circuit established by a sub-station and for automatically closing the prepared cir cuit of the next sub-station calling.

8. In a device of the character described, two series of signal members, a receiving station in which said signal members are located, and means for indicating the order in which one of said series of signal memhers is operated, said means adapted to establish an electric circuit through the other series of signal members in successive order and in the order in which the signal members of the first mentioned series were operated. v

9. In an intercommunicating telephone system a plurality of electric signal lights, means for closing an independent circuit through each light and a mechanism cooperating therewith adapted to indicate the order in which circuits are established through the signal lights when two or more circuits are closed substantially at the same time.

10. In an intercommunicating telephone system of the character described a series of electric signal lights, a second series of electric signal lights, means for establishing circuits through the first series of lights and means for successively establishing circuits subsequently through the second series of lights and in the order in which the circuits were established through the first named lights.

11. In an intercommunicating telephone system of the character described a series of electric signal lights, a second series of electric signal lights, means for successively establishing circuits through the second series of lights and inthe order in which the circuits are established through the first named lights, said means comprising a master switch arm, a plurality of secondary switch arms, one for eachjfirst named signal light, and means actuated by the establish ing of a circuit through any one of the first named signal lights for advancing the cooperating secondary switch arm and the master switch arm cooperating therewith, said means also adapted to arrange the secondary switch arms in a step-like formation to permit the establishment of consecu tive circuits through the second named signal lights.

12. In a system of the character described the combination with signal lights, of a mechanism for consecutively establishing circuits through said signal lights, said mechanism comprising a plurality of switch arms, a single master switch arm, means for arranging the first named switch arms in steplike formation to permit the establishment or" consecutive circuits through said switch arms and the master switch arm, and means for releasing each switch arm after a circuit has been established.

13. In a device of the character described a multiple switch comprising a master switch and a plurality oisecondary switches, means for imparting a step by step movement to the secondary switches and simultaneously a step by step movement to the master switch, and means preventing engagement of more than one secondary switch with the master switch at any one time.

14. In a device of the character described a multiple switch comprising a shaft, a plurality of interspaced ratchet gears secured thereon, a switch arm turnably mounted on the shaft adjacent each ratchet gear, a pawl on each switch arm, means for moving the pawls into and out of engagement with the respective ratchet gears and for simultaneously imparting a step by step rotary movement to the ratchet gears and the shaft upon which they are secured, and a master switch arm adapted to be engaged by said first named switch arms.

15. In a system of the character described, the combination of a plurality of sub-stations, a central station, a series of lights in the central station for indicating the number of calls entered and unattended to, and a second series of lights for indicating the order in which the calls were entered.

16. In a system of the character described, the combination of a plurality of sub-stations, a central station, a series of signal devices in the central station for indicating the number oil. calls entered and unattended to, and a second series'oil signal devices for ind cating the order in which the calls were entered.

17. In a system of the character described,

the combination of a plurality of sub-stations, a central station, a light and relay magnet inthe central station for each substation and adapted to be connected in circuit with the corresponding substation as a call is entered, a circuit controlled by each of said relay magnet-s, magnets in said latter Qircuits, switch arms, means operated by said latter magnets for advancing their corresponding switch arms, and means for advancing each operated switch arm upon op eration of another switch arm.

18. In a system of the character described, the combination 01" a plurality of sub-stations, a central station, a light and relay magnet in the central station for each substation adapted to be connected in circuit with the corresponding sub-station as a call is entered, a circuit controlled by each of said relay magnets, magnets in said latter circuits, switch arms controlled by said latter magnets, and a switch. member com mon to said switch arms.

19. In a system of the character described, the combination of a plurality of substations, a central station, a light and relay magnet in the central station for each substation and adapted to be connected in circuit with the corresponding sub-station as a call is entered, a circuit controlled by each or said relay magnets, magnets in said latter circuits, switch arms controlled by said latter magnets, a switch member common to said switch arms, and means for interconnecting said arms to cause each operated switch arm to be advanced upon operation of another switch arm and to prevent simultaneous contact between a plurality of said switch arms and said switch member.

20. In a system of the character described, the combination of a plurality of sub-stations, a central station, a light and relay magnet in the central station "for each substation and adapted to be connected in circuit with the corresponding sub-station as a call is entered, a circuit controlled by each of said relay magnets, magnets in said latter circuits, a switch arm for each circuit, a common switch member, a shaft supporting said arms and member, a ratchet wheel for each arm, and means operated by said latter magnets for advancing said ratchet wheels and for permitting the corresponding arms to be connected to said ratchet wheels.

21. In a system of the character described, the combination of a plurality of sub-stations, a central station, a light and relay magnet in the central station for each substation and adapted to be connected in circuit with the corresponding sub-station as a call is entered, a circuit controlled by each of said relay magnets, magnets in said latter circuit-s, a switch arm for each circuit, a common switch member, a shaft supporting said arms and member, a ratchet wheel for each arm, spring means constantly tending to connect said arms with said wheels, means operated by said latter magnets for permitting said spring means to effect a connection between said arms and wheels, and means driven by said operated means for advancing said wheels.

ABRAHAM BLOCK. 

